i have had the same problem with 2 thermostats, white rogers 80 series. one was programmable, one was not. replacing the stat always fixed it, but on this last one i saw that the stat would raise the temp to match the set temp, shut off the oudside unit and keep the indoor blower going. thus the temp would have to drop again to kick on anymore heat. the stat should have run the temp up one degree and shut off everything, but something in the stat was doing 1 thing wrong. canceling a call for heat when the temp was matched. i have a tech question in to white rogers about it.